An Improved Method to Resolve Plant Saponins and Sugars by TLC

Colorimetric Detection of Class A Soybean Saponins by G-Quadruplex-Based Hybridization Chain Reaction

Soybean saponin is one of the important secondary metabolites in seeds, which has various beneficial physiological functions to human health. GmSg-1 gene is the key enzyme gene for synthesizing class A saponins. It is of great significance to realize the visual and rapid detection of class A saponins at the genetic level. The hybridization chain reaction (HCR) was employed to the visual detection of GmSg-1 gene, which was implemented by changing the length of the target fragment to 92 bp and using the hairpin probes we designed to detect the GmSg-1 ^a and GmSg-1 ^b genes. The best condition of HCR reaction is hemin (1.2 μM), Triton X-100 (0.002%), ABTS (3.8 μM), and H₂O₂ (1.5 mM). It was found that HCR has high specificity for GmSg-1 gene and could be applied to the visual detection of different soybean cultivars containing Aa type, Ab type, and Aa/Ab type saponins, which could provide technical reference and theoretical basis for molecular breeding of soybean and development of functional soybean products.

High-Throughput Screening and Characterization of a High-Density Soybean Mutant Library Elucidate the Biosynthesis Pathway of Triterpenoid Saponins

Triterpenes (C30) constitute one of the diverse class of natural products with potential applications in food, cosmetic and pharmaceutical industries. Soyasaponins are oleanane-type triterpenoids widespread among legumes and particularly abundant in soybean seeds. They have associated with various pharmacological implications and undesirable taste properties of soybean-based food products. Uncovering the biosynthetic genes of soyasaponins will provide new opportunities to control the pathway for human benefits. However, the pathway of soyasaponin biosynthesis has not been fully elucidated in part because of a paucity of natural mutants. Here, we applied a structured high-density soybean mutant library for the forward genetic screening of triterpenoid biosynthesis. The seed soyasaponin polymorphism in the mutant library was evaluated using a high-throughput thin-layer chromatography and liquid chromatography tandem mass spectrometry analysis. This screening identified 35 mutants (3.85% of 909 mutant lines) with seven unusual soyasaponin phenotypes (Categories 1-7), which was greater than the number of natural mutants reported previously (22 mutants, 0.18% of ∼12,428 accessions). Nine unique intermediates of soyasaponin biosynthesis were identified and their chemical structures were estimated based on their MS/MS fragment patterns. Based on published information, 19 mutants could be associated with loss of function of four individual soyasaponin biosynthesis genes identified through expressed sequence tag mining or positional cloning, whereas the remaining 16 mutants were novel and may facilitate discovery of the unknown biosynthetic genes of soyasaponins. Our approach and library may help to identify new phenotype materials and causative genes associated with specialized metabolite production and other traits.

Biosynthesis of DDMP saponins in soybean is regulated by a distinct UDP-glycosyltransferase

2,3-Dihydro-2,5-dihydroxy-6-methyl-4H-pyran-4-one (DDMP) saponins are one of the major saponin groups that are widely distributed in legumes such as pea, barrel medic, chickpea, and soybean. The steps involved in DDMP saponin biosynthesis remain uncharacterized at the molecular level. We isolated two recessive mutants that lack DDMP saponins from an ethyl methanesulfonate-induced mutant population of soybean cultivar Pungsannamul. Segregation analysis showed that the production of DDMP saponins is controlled by a single locus, named Sg-9. The locus was physically mapped to a 130-kb region on chromosome 16. Nucleotide sequence analysis of candidate genes in the region revealed that each mutant has a single-nucleotide polymorphism in the Glyma.16G033700 encoding a UDP-glycosyltransferase UGT73B4. Enzyme assays and mass spectrum-coupled chromatographic analysis reveal that the Sg-9 protein has glycosyltransferase activity, converting sapogenins and group B saponins to glycosylated products, and that mutant proteins had only partial activities. The tissue-specific expression profile of Sg-9 matches the accumulation pattern of DDMP saponins. This is the first report on a new gene and its function in the biosynthesis of DDMP saponins. Our findings indicate that Sg-9 encodes a putative DDMP transferase that plays a critical role in the biosynthesis of DDMP saponins.

Functional characterization of naturally occurring wild soybean mutant (sg-5) lacking astringent saponins using whole genome sequencing approach

Triterpenoid saponins are one of the most highly accumulated groups of functional components in soybean (Glycine max) and the oxidative reactions during their biosynthesis are required for their aglycone diversity. Natural mutants of soyasaponins in wild soybean (Glycine soja) are valuable resources for establishing the soyasaponin biosynthesis pathway and breeding new soybean varieties. In this study, we investigated the genetic mechanism behind the absence of group A saponins in a Korean wild soybean mutant, CWS5095. Whole genome sequencing (WGS) of CWS5095 identified four point mutations [Val6 → Asp, Ile231 → Thr, His294 → Gln, and Arg376 → Lys] in CYP72A69 (Glyma15g39090), which oxygenate the C-21 position of soyasapogenol B or other intermediates to produce soyasapogenol A, leading to group A saponin production. An in vitro enzyme activity assay of single-sited mutated clones indicated that the Arg376 > Lys mutation (a highly conserved mutation based on a nucleotide change from G → A at the 1,127th position) may lead to loss of gene function in the sg-5 mutant. A very high normalized expression value of 377 reads per kilo base per million (RPKM) of Glyma15g39090 in the hypocotyl axis at the early maturation seed-development stage confirmed their abundant presence in seed hypocotyls. A molecular dynamics analysis of the Arg376 > Lys mutation based on the CYP3A4 (a human CYP450) protein structure found that it was responsible for the increase in axis length toward the heme (active site), which is critically important for biological activity and ligand binding. Our results provide important information on how to eradicate bitter and astringent saponins in soybean by utilizing the reported mutation in Glyma15g39090, and its importance for seed hypocotyl development based on transcript abundance.

Molecular elucidation of a new allelic variation at the Sg-5 gene associated with the absence of group A saponins in wild soybean

In soybean, triterpenoid saponin is one of the major secondary metabolites and is further classified into group A and DDMP saponins. Although they have known health benefits for humans and animals, acetylation of group A saponins causes bitterness and gives an astringent taste to soy products. Therefore, several studies are being conducted to eliminate acetylated group A saponins. Previous studies have isolated and characterized the Sg-5 (Glyma.15g243300) gene, which encodes the cytochrome P450 72A69 enzyme and is responsible for soyasapogenol A biosynthesis. In this study, we elucidated the molecular identity of a novel mutant of Glycine soja, 'CWS5095'. Phenotypic analysis using TLC and LC-PDA/MS/MS showed that the mutant 'CWS5095' did not produce any group A saponins. Segregation analysis showed that the absence of group A saponins is controlled by a single recessive allele. The locus was mapped on chromosome 15 (4.3 Mb) between Affx-89193969 and Affx-89134397 where the previously identified Glyma.15g243300 gene is positioned. Sequence analysis of the coding region for the Glyma.15g243300 gene revealed the presence of four SNPs in 'CWS5095' compared to the control lines. One of these four SNPs (G1127A) leads to the amino acid change Arg376Lys in the EXXR motif, which is invariably conserved among the CYP450 superfamily proteins. Co-segregation analysis showed that the missense mutation (Arg376Lys) was tightly linked with the absence of group A saponins in 'CWS5095'. Even though Arg and Lys have similar chemical features, the 3D modelled protein structure indicates that the replacement of Arg with Lys may cause a loss-of-function of the Sg-5 protein by inhibiting the stable binding of a heme cofactor to the CYP72A69 apoenzyme.

Commiphora leptophloeos Phytochemical and Antimicrobial Characterization

Commiphora leptophloeos is a plant specie usually known for its medicinal purposes in local communities in Northeast Brazil. In order to evaluate its therapeutic potential, we aimed to determine the phytochemical and antimicrobial properties of C. leptophloeos extracts. Thin Layer Chromatography (TLC) was able to detect the presence of phenolic compounds, flavonoids and reducing sugars. Three phenolic compounds were identified by HPLC and described as Gallic, Chlorogenic and Protocatechuic acids. On the other hand, H1NMR analysis revealed the presence of hinokinin, a bioactive lignan further characterized in the present work. The minimum inhibitory concentration (MIC) values for hinokinin ranged from 0.0485 to 3.125 mg/mL in different S. aureus clinical isolates and showed a bactericidal activity against MRSA isolated from blood (MMC 0.40 mg/mL) and postoperative secretion (MMC = 3.125 mg/mL). C. leptophloeos extracts also showed antimicrobial activity against Mycobacterium species such as M. smegmatis (MIC = 12.5 mg/mL) and M. tuberculosis (MIC = 52 mg/mL). Additionally, we determined the toxicity of C. leptophloeos by in vitro HC50 tests with hemolytic activity detected of 313 ± 0.5 μg/mL. Our results showed that C. leptophloeos possesses inhibitory properties against MRSA as well as several other clinically important microorganisms. Furthermore, the present work is the first report of the presence of hinokinin in Commiphora genus.

Comparison of saponin composition and content in wild soybean (Glycine soja Sieb. and Zucc.) before and after germination

Eight wild soybean accessions with different saponin phenotypes were used to examine saponin composition and relative saponin quantity in various tissues of mature seeds and two-week-old seedlings by LC-PDA/MS/MS. Saponin composition and content were varied according to tissues and accessions. The average total saponin concentration in 1 g mature dry seeds of wild soybean was 16.08 ± 3.13 μmol. In two-week-old seedlings, produced from 1 g mature seeds, it was 27.94 ± 6.52 μmol. Group A saponins were highly concentrated in seed hypocotyl (4.04 ± 0.71 μmol). High concentration of DDMP saponins (7.37 ± 5.22 μmol) and Sg-6 saponins (2.19 ± 0.59 μmol) was found in cotyledonary leaf. In seedlings, the amounts of group A and Sg-6 saponins reduced 2.3- and 1.3-folds, respectively, while DDMP + B + E saponins increased 2.5-fold than those of mature seeds. Our findings show that the group A and Sg-6 saponins in mature seeds were degraded and/or translocated by germination whereas DDMP saponins were newly synthesized.

Biennial review of planar chromatography: 2011–2013

The most important advances in planar chromatography published between November 1, 2011 and November 1, 2013 are reviewed in this paper. Included are an introduction to the current status of the field; student experiments, books, and reviews; theory and fundamental studies; apparatus and techniques for sample preparation and TLC separations (sample application and plate development with the mobile phase); detection and identification of separated zones (chemical and biological detection, TLC/mass spectrometry, and TLC coupled with other spectrometric methods); techniques and instruments for quantitative analysis; preparative layer chromatography; and thin layer radiochromatography. Numerous applications to a great number of compound types and sample matrices are presented in all sections of the review.